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Ankylosaurid tail club evolution

Ben Creisler

A new paper:

Victoria M. Arbour and Philip J. Currie (2015)
Ankylosaurid dinosaur tail clubs evolved through stepwise acquisition
of key features.
Journal of Anatomy (advance online publication)
DOI: 10.1111/joa.12363

Ankylosaurid ankylosaurs were quadrupedal, herbivorous dinosaurs with
abundant dermal ossifications. They are best known for their
distinctive tail club composed of stiff, interlocking vertebrae (the
handle) and large, bulbous osteoderms (the knob), which may have been
used as a weapon. However, tail clubs appear relatively late in the
evolution of ankylosaurids, and seemed to have been present only in a
derived clade of ankylosaurids during the last 20 million years of the
Mesozoic Era. New evidence from mid Cretaceous fossils from China
suggests that the evolution of the tail club occurred at least 40
million years earlier, and in a stepwise manner, with early
ankylosaurids evolving handle-like vertebrae before the distal
osteoderms enlarged and coossified to form a knob.